<nz-select [(ngModel)]="classId" name="class" [nzDisabled]="isPreView" [nzPlaceHolder]="className ? className : '选择班级'"
  [nzShowSearch]="true" nzAllowClear (ngModelChange)="ngModelChange($event)">
  <nz-option *ngFor="let class of classList" [nzValue]="class.id" [nzLabel]="class.name">
  </nz-option>
</nz-select>
